1. Field of the Invention
The present invention generally relates to optical plates, and more particularly to an optical plate for use in, for example, a liquid crystal display (LCD).
2. Discussion of the Related Art
The weight and thinness of LCD panels make them suitable for a wide variety of uses in electronic devices such as personal digital assistants (PDAs), mobile phones, portable personal computers, and other electronic appliances. Liquid crystal is a substance that does not illuminate light by itself. Instead, the liquid crystal relies on light received from a light source in order for the liquid crystal to display information. In a typical liquid crystal display device, a backlight module powered by electricity supplies the needed light.
FIG. 5 is a cross-section of an exploded side view of a typical backlight module 10 employing a typical optical diffusion plate. The backlight module 10 includes a housing 11, a plurality of lamps 12 disposed in the housing 11, a light diffusion plate 13 and a prism sheet 14. The light diffusion plate 13 and the prism sheet 14 are stacked on the housing 11 in that order. The lamps 12 emit light, and the inside walls of the housing 11 are configured for reflecting some of the light upwards. The light diffusion plate 13 includes a plurality of embedded dispersion particles. The dispersion particles are configured for scattering received light, and thereby enhancing the uniformity of light that exits the light diffusion plate 13. The prism sheet 14 includes a plurality of V-shaped structures on a top thereof. The V-shaped structures are configured for collimating, to a certain extent, the received light.
In use, light emitted from the lamps 12 enters the prism sheet 14 after being scattered in the diffusion plate 13. The light is refracted by the V-shaped structures of the prism sheet 14 and is thereby concentrated, so that a brightness of light illumination is increased. Finally, the light propagates into an LCD panel (not shown) disposed above the prism sheet 14. The brightness of light illumination may be improved by the V-shaped structures of the prism sheet 14, but the viewing angle may be narrow. In addition, although the diffusion plate 13 and the prism sheet 14 are in contact with each other, a plurality of air pockets still exists at the boundary therebetween. When the backlight module 10 is in use, light passes through the air pockets, and some of the light undergoes total reflection at one or another of the corresponding boundary. As a result, the light energy utilization ratio of the backlight module 10 is reduced.
Therefore, a new optical means is desired in order to overcome the above-described shortcomings.